I'm still waiting for the release in my country, but it seems to be quite nice, like a high graphic DoTA. I don't know if you've played it often but how long would a normal match take on average?

My limited experience in the game (I've only played a few matches, game isn't that appealing to me, unfortunately), matches can last a lot longer. Especially if both teams are about evenly matched.

One battle I played against the computer lasted over 40 minutes, I think? Depending on your skill level (and if online, enemy skill level), and settings, I imagine games can last anywhere from sub 10 minutes, to multiple hours, possibly even a stalemate. I dunno if there is a time limit option though.